© 2017 American Dental Association Background Cracked teeth are ubiquitous in the adult dentition. The objective of this study was to determine which patient traits and behaviors and external tooth and crack characteristics correlate with cracked teeth being symptomatic. Methods Dentists in The National Dental Practice-Based Research Network enrolled a convenience sample of patients each with a single, vital posterior tooth with at least 1 observable external crack in this observational study; they enrolled 2,975 cracked teeth from 209 practitioners. The authors collected data at the patient level, tooth level, and crack level. They used generalized estimating equations to obtain significant (P <.05) independent odds ratios (OR) associated with teeth that were symptomatic for a crack. Results Characteristics positively associated with cracked tooth symptoms, after adjusting for demographics, included patients who clenched, ground, or pressed their teeth together (OR, 1.30; 95% confidence interval [CI], 1.12-1.50), molars (OR, 1.58; 95% CI, 1.30-1.92), teeth with a wear facet through enamel (OR, 1.22; 95% CI, 1.01-1.40), carious lesions (OR, 1.31; 95% CI, 1.07-1.60), cracks that were on the distal surface of the tooth (OR, 1.31; 95% CI, 1.13-1.52), and cracks that blocked transilluminated light (OR, 1.31, 95% CI, 1.09-1.57). Teeth with stained cracks were negatively associated with having cracked tooth symptoms (OR, 0.68; 95% CI, 0.55-0.84). Conclusions The greatest likelihood of a cracked tooth being symptomatic was found when patients reported clenching or grinding their teeth and had a molar with a distal crack that blocked transilluminated light. Practical Implications This information can help inform dentists in the decision-making process regarding the prognosis for a cracked tooth.